While initially developed as a means for communicating the “online status” in instant messaging applications, presence has become a key enabler of web-based content provider converged applications (for example, GOOGLE TALK® and SKYPE® applications), enterprise converged applications (for example, SAMETIME® application) and service provider/telephone company converged applications (for example, Push-to-talk applications). GOOGLE TALK is a registered trademark of Google Inc. in the United States and other countries. SKYPE is a registered trademark of Skype Limited Corp. in the United States and other countries. SAMETIME is a registered trademark of International Business Machines Corp. in the United States and other countries.
Presence, broadly defined as an event publish-notification infrastructure for converged applications, has emerged as a key mechanism for collecting and disseminating context attributes for next-generation services in both enterprise and provider domains. Presence can be viewed as the ability of a communications infrastructure to both track and disseminate a variety of dynamic attributes of individuals, objects and/or devices. Common examples of presence information include but are not limited to a status update on a social network (as for example “user A is away”) and/or a location update for an object (as for example “taxi 123” is now located in “geographic area A”). Given the large amount of presence information available and its apparent usefulness in a variety of contexts, obtaining, organizing and disseminating presence information in useful ways is highly desirable.